1. Field of the Invention
The present invention relates to an analog/digital signal processor and an analog/digital signal processing method, and more particularly, to an analog/digital signal processor such as a multi-purpose digital set-top box and an analog/digital signal processing method which can simply output externally-input analog signals without eliminating additional data such as copy protection data included in the externally-input analog signals.
2. Description of the Related Art
FIG. 1 is a block diagram illustrating a conventional multi-purpose digital set-top box.
A digital set-top box 10 includes a broadcasting signal receiving unit 102 receiving broadcasting signals such as ground wave broadcasting signals, satellite broadcasting signals, cable broadcasting signals, etc. and outputting the received broadcasting signals as analog broadcasting signals or digital broadcasting signals under the control of a control unit 116, an MPEG-2 encoder 104 converting the analog broadcasting signals output from the broadcasting signal receiving unit 102 and the analog signals received through an external analog signal input appliance such as a DVD player into digital signals of MPEG-2 transport streams, a digital communication unit 106 outputting the MPEG-2 transport streams output from the broadcasting signal receiving unit 102 and the MPEG-2 encoder 104 to an external display appliance such as a digital TV, an MPEG-2 decoder 108 converting the MPEG-2 transport streams output from the broadcasting signal receiving unit 102 and the MPEG-2 encoder 104 as analog signals and outputting the converted analog signals under the control of the control unit 116, an analog communication unit 110 outputting the analog signals output from the MPEG-2 decoder 108 to an external analog playback appliance such as an analog TV or a VCR, a channel selecting unit 112 receiving the selected channel and outputting the received channel to the control unit 116 when a user selects a predetermined channel through channel selection and an input device such as a remote control, a channel map memory 114 storing data on the broadcasting channels selected by a viewer, and a control unit 116 controlling a broadcasting signal process according to the type of broadcasting signal received from the broadcasting signal receiving unit 102 with reference to the channel map memory 114 based on channel selection signals from the channel selecting unit 112 and controlling operations of other elements of the digital set-top box 10.
When a viewer selects a desired broadcasting channel through the remote control, the channel selecting unit 112 transmits the selected broadcasting channel to the control unit 116. The control unit 116 determines the type of the selected broadcasting channel and whether the selected broadcasting channel transmits analog signals or digital signals with reference to the channel map memory 114, and controls operations of the broadcasting signal receiving unit 102.
A network information table (NIT) and a bouquet association table (BAT) are stored to a memory of the set-top box for receiving digital broadcasting, so that the control unit can read physical data and service data of the channel. The channel map memory 114 can additionally store the physical data and the service data of analog broadcasting signals to the NIT and the BAT. Further, the channel map memory 114 includes data on whether broadcasting channels transmit digital signals or analog signals. However, in order to simplify the set-top box, it is possible to exclude the channel selecting unit 112 and the channel map memory 114 from the set-top box, and transmit the selected channel data among channel data stored to an external display appliance such as a digital TV, etc., to the set-top box through the digital communication unit 106. In the meantime, the set-top box 10 may further comprise an MPEG-2 transport stream parsing unit for parsing MPEG-2 transport streams to audio signals and video signals and outputting the parsed audio signals and video signals. However, it helps to reduce a radio network load to transmit not the parsed data but the MPEG-2 transport streams for transmitting data to the digital TV by using radio communication channels.
The broadcasting signal receiving unit 102 comprises a tuner unit (not shown) for selecting ground wave broadcasting, satellite broadcasting, and cable broadcasting by a viewer's selection and converting signals of the selected broadcasting into intermediate frequency signals, and a demodulation unit (not shown) for executing a predetermined demodulation by selecting the tuner unit. The broadcasting signal receiving unit 102 outputs demodulated signals into analog signals when broadcasting signals are analog signals, and outputs demodulated signals to digital signals of the MPEG-2 transport streams when broadcasting signals are digital signals.
In the meantime, a DVD player executes a copy protection process such as macrovision for copyright protection ordinarily when outputting data of a DVD that is a digital recording medium. When externally-input analog signals that have gone through a macrovision process pass through the MPEG-2 encoder, copy protection signals disappear, so that the macrovision process is meaningless.
Therefore, in order to solve the aforementioned problem, elimination of copy protection signals may be prevented by using an encoding method suitable for analog signals that have gone through the macrovision process by adding a macrovision detection function to the MPEG-2 encoder 104.
However, since such a method should additionally perform an operation for detecting analog signals that have gone through the macrovision process and an encoding operation suitable for analog signals that have gone through the macrovision process, there is a problem in that a structure of the set-top box becomes overly complicated.